Ros1 is a receptor tyrosine kinase closely related to the ALK and LTK kinases based on sequence similarity of their kinase domains. The Ros1 protein is composed of an extracellular domain containing several fibronectin-like repeats and a cytoplasmic kinase domain. The function of Ros1 has not been fully elucidated, but the presence of fibronectin domains suggests a role in cell adhesion or interactions with the extracellular matrix. However, endogenous Ros1 ligands have not yet been identified. Its expression in adult humans has been detected in several tissues, such as the kidney, cerebellum, and gastrointestinal tract, but appears to be low or absent in other tissues. Its expression in the developing kidney and intestine suggests that it may have a role in epithelial-mesenchymal transition. ROS1 deficient mice are healthy and viable, but males are infertile due to defects in the epididymis that result in incomplete spermatocyte maturation.
Several distinct genomic rearrangements involving ROS1 have been detected in a variety of cancers including non-small cell lung cancer (NSCLC), glioblastoma, cholangiocarcinoma, colorectal cancer, gastric adenocarcinoma, ovarian cancer, angiosarcoma, epithelioid hemangioendothelioma, melanoma, and inflammatory myofibroblastic tumors. These rearrangements result in proteins that contain the C-terminal kinase domain of Ros1 fused to the N-terminal domains of a number of different unrelated proteins. Several of these fusion proteins have been shown to be oncogenic. Expression in fibroblasts promotes their proliferation, growth in soft agar, and ability to form tumors in mice. Expression in murine Ba/F3 cells renders them independent of IL-3 for growth and promotes their ability to form tumors in mice (Takeuchi K, et al., Nat Med. 2012, 18:378-81; Gu T L, et al., PLoS One 2011, 6:e15640). The rate of oncogenic Ros1 fusions is generally low, ranging from 1-2% in NSCLC (Kim M H, et al., Lung Cancer 2014, 83:389-95; Takeuchi K, et al., Nat Med. 2012, 18:378-81; Davies K D, et al., Clin Cancer Res. 2012, 18:4570-9; Li C, et al., PLoS One 2011, 6:e28204; Rimkunas V M, et al., Clin Cancer Res. 2012, 18:4449-57), but may be relatively high in other cancers, up to 9% in cholangiocarcinoma (Gu T L, et al., PLoS One 2011, 6(1):e15640) and 17% in spitzoid (melanoma) tumors (Wiesner T, et al., Nat Commun. 2014, 5:3116).
Because of the similarity between ALK and Ros1 kinase domains, many ALK inhibitors also inhibit Ros1. Ros1 inhibition negatively affects proliferation of engineered Ba/F3 cells expressing Ros1 fusion proteins as well as the proliferation of NSCLC patient derived HCC78 cells that harbor a SLC34A2-ROS1 fusion. Ros1 inhibition also negatively affects growth of engineered Ba/F3 and HEK293 tumors containing Ros1 fusion proteins in mice.
Recently, a number of inhibitors described to have activity on Ros1 have entered clinical testing. The first, crizotinib (Xalkori®), has been shown to reduce tumors and significantly prolong survival in patients with ROS1 rearrangements. However, following an initial response, resistance is seen and in one report this has been linked to a G2032R mutation in the Ros1 kinase domain that is expected to affect crizotinib binding.
WO-2004/058176 discloses acyclic pyrazole compounds for the inhibition of mitogen activated protein kinase-activated protein kinase-2.
J. Med. Chem., 2011, 54, 5820-5835 discloses pyrazolo derivatives as phosphodiesterase subtype-10 inhibitors.
WO-2009/086129 relates generally to pyrazolo [1,5-a] pyrimidine-based modulators of Liver X receptors.
WO-2009/108838 relates to pyrazolo[1,5-a]pyrimidine compositions that are useful for inhibiting abnormal growth of certain cell types.
EP1505068 relates to pyrazolo-[1,5-a]-pyrimidine derivatives and analogues as NAD(P)H oxydase inhibitors.
WO-2004/017908 provides a calcium receptor modulator.
There is thus a strong need for novel Ros1 kinase inhibitors thereby opening new avenues for the treatment or prevention of cancer, in particular non-small cell lung cancer (specifically adenocarcinoma), cholangiocarcinoma, glioblastoma, colorectal cancer, gastric adenocarcinoma, ovarian cancer, angiosarcoma, epithelioid hemangioendothelioma, inflammatory myofibroblastic tumors, breast cancer and chronic myelogenous leukemia. In a particular embodiment, there is a need for Ros1 kinase inhibitors that are not affected by mutations that abrogate inhibition of the first wave of Ros1 inhibitors.
It is accordingly an object of the present invention to provide such compounds.